1. Field of the Invention
The present invention relates to a defect inspection method and a defect inspection apparatus. Particularly, the present invention relates to a technology suitable for inspecting defects such as contaminating of foreign matters occurring in manufacturing processes, such as a semiconductor device manufacturing process, a liquid crystal display device manufacturing process and a printed circuit board manufacturing process, for manufacturing a product by forming a pattern on a substrate while detecting and analyzing the defects to take a countermeasure against the defects.
2. Description of the Related Art
In a semiconductor device manufacturing process, if there are foreign matters on a substrate (a wafer), the foreign matters pose a cause of defects such as defective electrical insulation and short circuits between interconnections. With the advancement of miniaturization of semiconductor devices, even finer foreign matters on a semiconductor device pose a cause of defective electrical insulation of its capacitor, or a cause of destruction of a gate oxide film and the like. Foreign matters are various. Some come from moving parts in the conveying equipment and the bodies of workers, and some are produced through chemical reaction of process gases in processing apparatuses. Others are contaminants in chemicals and materials used for manufacturing semiconductor devices.
A similar problem takes place in the liquid crystal display device manufacturing process. If foreign matters adhere onto, or some defect takes place in, a pattern formed on a liquid crystal display device substrate, the display device on the substrate becomes unusable any more. This is also the case with the printed circuit board manufacturing process. Adherence of foreign matters to the pattern poses a cause of short circuits and defective electrical connections in the pattern.
In the field of technology for detecting such foreign matters on a substrate to be inspected, Japanese Unexamined Patent Application Publication No. Sho. 62-89336 discloses the following technique. This patent document describes its technique as enabling highly reliable and sensitive inspection of foreign matters and defects while avoiding a false reporting that might be caused by a pattern. More specifically, foreign matters and defects are detected by irradiating the substrate with a laser beam, by detecting light scattering from foreign matters if the foreign matters adhere onto the substrate, and accordingly by comparing the result of the current detection with the result of the immediately preceding detection for another substrate of the same type. As well, Japanese Unexamined Patent Application Publication No. Sho. 63-135848 discloses a technique of irradiating a substrate with a laser beam, thus by detecting light scattering from foreign matters if the foreign matters adhere onto the substrate, and accordingly by analyzing the foreign matters thus detected by use of a technique of analyzing laser photoluminescence, a technique of analyzing two-dimensional X-ray magnetic resonance (XMR), or the like.
In another disclosed technique for inspecting foreign matters, a wafer is irradiated with coherent light, a spatial pattern removes light reflected from a repeated pattern on the wafer, and thereby foreign matters and defects, which do not appear repeatedly, are showed up and thus detected. In addition, Japanese Unexamined Patent Application Publication No. Hei. 1-117024 discloses a foreign matter inspecting apparatus designed to irradiate a circuit pattern formed on a wafer with light in a direction tilted at an angle of 45° to a main group of straight lines in the circuit pattern, and thereby preventing zeroth-order diffracted light, which comes from the main group of straight lines, from entering an aperture of its detection lens. This patent document also discloses that light from groups of straight lines, other than the main group of straight lines, are blocked by use of a spatial filter. As for an existing technique concerning an apparatus and a method for inspecting defects such as foreign matters, Japanese Patent Application Publication No. 2000-105203 discloses that a detection pixel is changed in size by switching detection optical systems. A technique for measuring the sizes of foreign matters is disclosed in each of Japanese Patent Application Publications Nos. 2001-60607 and 2001-264264. In a technique for detecting defects on a thin film, disclosed in Japanese Patent Application Publication No. 2004-177284, a beam spot oblong in a direction perpendicular to a direction in which the stage travels is formed on the thin film by focusing a laser light beam on the thin film, and the defects are detected in a direction perpendicular to the lighting direction.